BRAINCAKEHistone Acetylation
Histones are positively charged proteins. DNA is negatively charged because of its phosphate groups, so DNA is attracted to histones and wraps around them. How tightly it is held depends on the chemical groups attached to the histones.
Acetylation is the addition of an acetyl group (COCH3) to a histone. The acetyl group, donated by a molecule called acetylcoenzyme A, reduces the positive charge on the histone. The histone then binds the DNA less tightly, the chromatin becomes less condensed, and transcription factors and RNA polymerase can reach the DNA, so the gene can be transcribed.
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All 18 lessons in Control of Gene Expression · All AQA A-level Biology topics